This invention relates generally to injection molding apparatus and more particularly to apparatus in which removable inserts seated in a melt distribution manifold are each accurately aligned by a pin extending outwardly in alignment with a melt duct inlet.
Multi-cavity injection molding systems having a heated melt distribution manifold are well known. The melt distribution manifold has a melt passage with a number of branches extending outwardly from a common inlet portion to convey melt to a number of spaced heated nozzles. The melt duct in each nozzle extends at 90.degree. to the respective branch of the melt passage in the melt distribution manifold, and the flow of melt through each branch and nozzle must be balanced and sharp corners or edges which produce shear stress in the flowing melt are unacceptable. It is also known to provide removable inserts or plugs seated in transverse openings in the melt distribution manifold in alignment with the nozzles. Each insert has a melt duct with a smoothly curved bend extending through 90.degree. from an inlet in alignment with the respective branch of the melt passage in the melt distribution manifold to an outlet in alignment with the melt duct through the respective nozzle. The melt duct inlet extends through a cylindrical portion of the outer surface of the insert and must be very accurately aligned with the respective branch of the melt passage in the melt distribution manifold to avoid unacceptable shear stress in the flowing melt.
As seen in Mold-Masters Limited Canadian Patent Application Serial Number 2,047,461 Laid-Open Jan. 20, 1993, entitled "Injection Molding Manifold with Removable Inserts", these previous inserts are aligned in the opening by a pin extending outwardly from a bore in a flange portion of the insert. The problem with these previous inserts is that it is extremely difficult to reliably align the melt duct inlet with the respective branch of the melt passage with sufficient accuracy to avoid producing shear stress in the flowing melt. The pin is received in a bore in the flange portion of the insert, and the difficulty is in drilling the bore in the required position with sufficient accuracy. Any resulting misalignment of the insert cannot be determined during installation, but after the system is operating a slight misalignment of any one of the inserts in the system produces product of unacceptable quality and requires a very costly shut down of the system. This problem has resulted in limited use of the previous inserts.
Also, in the past, various separate means have been required to accurately locate the melt distribution manifold with respect to the mold.